1. Field of the Invention
The invention relates to determining concentrations of molecular gaseous species exhaled by subjects receiving pressure support therapy.
2. Description of the Related Art
Systems that provide pressure support to a subject are known. Some conventional systems are configured to estimate the concentration of one or more gaseous molecular species in gas expired by the subject to determine the effectiveness of the therapy and/or to titrate the therapy.
In spontaneously breathing, non-intubated subjects, determining the concentration of one or more gaseous molecular species in expired gas is difficult because expired gas is subject to dilution. The dilution may be caused by gas provided by the pressure support system during expiration. Increased leaks to the ambient atmosphere require increased gas to be provided as part of pressure support therapy during expiration causing increased dilution.